This invention relates to rolling door assemblies and in particular such assemblies wherein the rolling door comprises a flexible curtain connected at the top or inner end to a rotatable curtain roll.
The use of rolling doors, particularly for industrial and commercial applications, is well known. These doors can be of various constructions including flexible doors made from relatively thin plastic or fabric sheets. Generally the door is rolled up about a horizontal roll or shaft extending across the top of the door opening. In some cases the roll for the curtain can be spring loaded in order to counter balance the door and overcome gravitational forces acting on the door so it will open with relative ease. It is common to provide an electric operator including an electric motor to open and close the door. Generally this operator rotates the curtain roll at a constant rate of speed. Vertical guide channels are generally provided along the sides of the doorway to accommodate the edges of the flexible door.
U.S. Pat. No. 4,690,195, issued Sep. 1, 1987 to Douglas B. Taylor teaches an operating mechanism for a rolling door having power operated means for rolling up and rolling down the door. In one version there is a drive gear for the door shaft which supports the rolling door and a further drive gear for a idler shaft which helps to feed the flexible rubber curtain into its guide channels. These drive gears are floatingly mounted on the respective shafts for free rotation. By means of a dog and pin arrangement, means are provided for accommodating excess winding and unwinding forces which develop in this system as a result of a variation in the actual linear velocity of travel of the bottom or outer end portion of the curtain during unwinding and winding operations. This variation in linear velocity arises from the variation in the diameter of the windings of the rolled door on the door shaft as it is rotated while the speed of rotation of the door shaft itself is constant. There are several difficulties with this known arrangement including the need for an idler roll and the need to precisely locate the dog member and pin associated with each shaft to ensure that engagement and positive drive only occur at the appropriate times.
A simpler arrangement for accommodating the variation in speed of a roll up door is disclosed in copending Canadian patent application Ser. No. 554,847 filed Dec. 18, 1987 by the present applicant. In this known arrangement, there is an idler drive member supported about the idler or guide roll of the roll door assembly. An adjusting element including a coil spring is provided and is capable of accommodating the differences in the turning forces developed at the idler drive member and at the idler or guide roll. This adjusting element is connected between the idler drive member and the idler or guide roll.
While this known arrangement may be suitable for thicker flexible curtains which generally require the use of an idler roll in order to feed the curtain into its guide channels, it is not entirely suitable for other applications and has some disadvantages. For example many rolling door assemblies now in the market employ thin flexible curtains have a thickness of about 1/8' and such curtains often do not require the use of an idler roll. Because the curtain is quite thin, the diameter of the rolled curtain is not necessarily substantial. The variation in the diameter of the rolled curtain that does occur as the curtain is unwound can generally be accommodated by the construction of the guide channels and the location of the door roll above the door opening. Also the operating life of the coil spring which forms the adjusting element in this known rolling door assembly is somewhat limited because the load or forces acting on the spring can be quite substantial. Further if the rolling door becomes disconnected from the two chain loop members that act to pull this rolling door downwards, due to an impact on the door or otherwise, it can require considerable time and skill to restore this rolling door assembly to proper working order.
It is an object of the present invention to provide a rolling door assembly that includes a flexible curtain mounted on a rotatable curtain roll and that has a simple and easy to construct adjusting mechanism that is connected between the outer or bottom end of the curtain and a drive mechanism for pulling the flexible curtain downwards. This adjusting mechanism accommodates a difference in speed of travel between the drive mechanism and the outer or bottom end of the curtain, the outer end moving at a variable speed as the curtain is wound up or unwound.
The preferred adjusting mechanism described and illustrated herein has a good operating lifetime and it avoids the need for counterbalance springs or counterweights often used in the past to ensure that a rolling door remains fully closed in the closed position.
A further advantage of the preferred rolling door assembly described herein is that, should the rolling door accidentally become detached from its drive mechanism due to an impact on the door or otherwise, it is a relatively quick and easy operation to reconnect the door curtain so that the door assembly is back in working order.